This invention relates to flocculation apparatus and to apparatus for floating upwardly in a liquid and for moving downwardly in the liquid under the influence of gravity.
By way of example, and to provide a background for the flocculation apparatus of the present invention, the processing of water to provide a supply of drinking water is a well developed technology. Typically with surface water supply systems, there is a multi-stage process for removing contaminants. Typically, the process first includes the stage of removing coarse debris from the water by screens or other mechanisms. This stage is typically followed by the several stages of conventional surface water treatment. In the first stage, chemicals are introduced into the water to separate particulate matter from the water. This stage is typically performed by the addition of chemicals to the water and then dispersion through rapid mixing. This stage is typically followed by flocculation to agglomerate the solid particles and this stage is typically followed by separation and removal of the solid particles by gravity in a sedimentation basin.
Mechanical devices have been employed for nearly 100 years in flocculator basins in municipal drinking water treatment plants. Different types of flocculator mechanisms have been typically employed.
The first type of mechanism has been a mechanically driven mechanism consisting of a series of wood, fiberglass or steel paddles. These paddles are powered in a circular, unidirectional motion through the water via a submerged xe2x80x9creelxe2x80x9d arrangement with a horizontal rotating shaft submerged in the basin. Radiating from the shaft is a steel structure which supports the paddles that rotate in a circular motion. In this mechanism, the shaft of the paddle mechanism is supported by a series of bearings which are submerged in the water. The drive unit is often non-submerged and is located in a dry well at the end of the basin or via a top mounted drive above the liquid level. This technology is widely used in water treatment plants.
Other types of circular mechanisms are also employed. These typically consist of paddles rotating in a circular, uni-directional motion mounted on a vertical shaft or turbine flocculators operating on the vertical shaft.
The above-noted flocculator mechanisms require either submerged bearings or a large number of drive units to accommodate flocculation in a basin.
Other types of flocculation mechanisms of a non-circular, bi-directional design, i.e., oscillating flocculators, are also known. The two types of these devices principally used are the Walking Beam flocculator and Floscillator. In both of these mechanisms, the paddles move in non-circular, linear motion, either up and down or back and forth in the flocculation basin. The principal advantage to this type of device is that it provides superior flocculation at a lower horsepower per unit volume input than circular mechanisms, and the mechanism can be designed without the use of submerged bearings for moving parts in the water other than the paddles. These designs are widely accepted and have been used in the United States municipal drinking water market for nearly 50 years. The principal disadvantage of these types of designs is that although these designs provide effective flocculation, they are expensive to manufacture due to the reciprocating movement that provides high torsional stresses to the components.
Accordingly, there is a need in the art for new and improved flocculation apparatus overcoming the above-noted disadvantages associated with prior art flocculation apparatus.
Numerous flotation apparatus are known to the art for the floating upwardly in a liquid and for moving downwardly in a liquid. However, it is believed that there is a need in the art for new and improved floatation apparatus which are useful in flocculation apparatus as well as in other applications.
It is the object of the present invention to satisfy the above needs in the art.
Flocculation apparatus satisfying such need and embodying the present invention may include paddle apparatus for being moved upwardly and downwardly through a liquid in which particles are suspended to facilitate agglomeration of the particles, flotation apparatus and compressed gas discharge apparatus for alternately and continuously moving the paddle apparatus upwardly and downwardly through the liquid in response to compressed gas being introduced continuously into the flotation apparatus and wherein the flotation apparatus are for continuously receiving the compressed gas and in response thereto for floating and moving the paddle apparatus upwardly through the liquid after which the compressed gas discharge apparatus are for discharging the compressed gas from the flotation apparatus to allow gravity to pull the paddle apparatus downwardly through the liquid, and which flocculation apparatus may further include a compressed gas supply for continuously introducing compressed gas into the flotation apparatus.
Flotation apparatus satisfying the foregoing need and embodying the present invention may include combination flotation and compressed gas discharge apparatus for receiving compressed gas and in response to sufficient compressed gas being received therein for becoming sufficiently buoyant to float upwardly in the liquid, and upon such combination flotation and compressed gas discharge apparatus floating sufficiently high in the liquid such combination apparatus automatically discharge sufficient of the compressed gas to cause the combination apparatus to lose sufficient buoyancy to permit gravity to pull the combination apparatus downwardly through the liquid.